Hi,
How can I solve this differential calculation in HP Prime?
z= 3x^2 - xy +y^2
Considering that (x, y) goes from (2,1) to (1.96,0.95).
I've made several attempts, but I can not enter the data correctly.
In this other POST (http://www.hpmuseum.org/forum/thread-7346.html), something similar happened, but Tim was able to enter the data correctly in LIMIT

If you do not specify a variable, then the default variable 'x' is used. For example, diff(x^2*y^3) returns 2x*y^3. So in your second attempt, it is not clear what you meant by the diff(diff(..)) operation since you did not specify a variable. Did you mean to compute \( \frac{\partial^2}{\partial x^2} (3x^2-xy+y^2) \) or did you intend to have something else?

In particular, if you have questions on how to use a command, consider using the built-in help:

1) type the command
2) with the cursor on the typed command name, press the help button

Usually, the help also provides examples of how to use the commands. For desolve, the help says: